1. Field of the Invention
The present invention relates to surgically implanted mammary expansive devices containing a biocompatable filler material inside a shell used for augmentation or reconstruction of breast tissue.
2. Description of the Related Art
Mammary prosthetic surgical implants are used to expand or to modify the volume or appearance of tissue in the area of the female breast.
Breast implants in current use consist of a flexible silicone rubber envelope or sack filled with salt and water solution called saline. In the past, implants filled with sticky silicone gel were commonly used in U.S., but the government restricted their use after there was concern about possible health problems attributed to silicone gel leaking from implants.
The saline-filled mammary implants commercially available in the U.S. are generally made by injecting saline into the shell through a port either at manufacturing plant site for fixed volume and predetermined size implants (non-inflatable) or in the operating room to the desired and adjustable sizes using serial progressive expanding injection technique, over the course of three to six months, while the implant is in the patient and everything is sewn closed (inflatable). The mammary tissue expanding surgical implant is used for restoring, improving, augmenting and reconstructing the female breast where the implant is placed under the breast tissue between the breast tissue and chest muscle or under the muscle itself.
The major problem that presents itself in the use of mammary prosthetic implants is that over time, the filler material tends to bleed and leak out of the shell causing deflation. For saline breast implant the leak is sudden and requires immediate implant removal or replacement.
Saline is considered harmless but of course, a leaky saline breast implant will need to be replaced by a new surgical operation since it will flatten like a deflated balloon.
Between Jan. 1, 1985, and Mar. 16, 1995, FDA received 19,296 adverse reports, including deflation, associated with saline breast implants. Furthermore, in 1995, Arthur P. Worseg, MD and co-workers published the study on 167 saline implants in 77 patients where the complete deflation was 22% from 1972 to 1984 and 26% from 1985 to 1992.
In addition to the major drawback of bleeding, published reports and studies are implicating the saline breast implants with other problems such as, wrinkling, folding, ridging, being less fleshy, not having shape memory and quick displacement of the saline solution and air present in the implant can create an audible sound or "slosh".
To overcome the saline drawbacks of wrinkling, folding, being less fleshy, having no holding power, and in general to improve overall acceptability of a saline-filled breast implant, researchers have focused attention on increasing saline consistency by mixing various kinds of polymeric water thickening or gelling agents with saline.
For example, U.S. Pat. No 4,138,382, to Polmanteer discloses a crosslinked water swellable or soluble gel as filling material for breast implant prosthesis. He also suggests placing insufficient amount of gel inside the shell where such a prosthesis can be implanted through a relatively small incision. Later-on after insertion, water can be added to increase the implant volume through swelling of gel filler material. Further, U.S. Pat. No 5,116,371, to Christensen, et al discloses a mammary prosthesis comprising a silicone outer container filled with hydrogel particles.
Thus, while providing clear advantages over simply implanting saline, all these new filler materials, with low or no crosslinking, are more or less soluble and are not able to retain or hold all the water within their loose polymeric structure resulting a blend of swollen and dissolved gel in free water. In this case, beside the possible seepage and transudation of loose gel or linear polymer through the shell, the free moving water is able to bleed out through the shell making a decrease in implant volume unavoidable after some time, requiring a new surgical operation to remove or replace deflated breast implant.
Thus, there is a great need to eliminate the problem of bleeding or leakage from mammary prosthesis, regardless of filler material considered to be harmless like saline or questionable like silicone gel, since a leaky implant needs to be replaced by a new surgical operation.
Accordingly, it would be a significant contribution to the medical device art to eliminate the major problem of bleeding or leakage and transudation from mammary prosthetic surgical implant by providing a non-bleeding harmless filler material capable of being used with existing mammary device manufacturing and breast surgical procedures practiced in the U.S. or elsewhere.